Planning to re-route breakaway wiring. This is a 5th with the switch mounted on the f-glass next to the pin box. I will drill a hole through the paneling. It's very thin (1/8" or less). What type of bitt will give the best (cleanest) hole? I plan a gradually increasing size up to about 1/2".
Grrrrrrrrr, posted in the wrong section. Figure the moderators will move it........

I've had very good luck with "brad point" bits. They're available at any woodworking store and at the big box hardware stores. They have a center point that keeps your hole right where you want it and the cutting starts out at the very edge of the bit, therefore it won't wander and you don't need to start with a small bit and work your way up to the 1/2" hole. Very clean cutting in wood, plastic, fiberglass, aluminum & brass. They WILL NOT work in ferris metals. The bits are too soft for steel or cast iron.

Locate your hole where you won't hit any framing members or anything important behind it and use a 1/2" brad point bit or forstner bit and make your hole in one shot...don't step it up. Hole saws work well on the thin fiberglass skin and will cut through anything below it including ferrous and non-ferrous metals, wood, electrical wiring, pipe, you name it. You may have difficulty finding a 1/2" hole saw, they usually start around 3/4". By the time you add a standard 1/4" pilot bit there wouldn't be much room left for the hole saw itself.

To reduce chipping of the gelcoat, cover the area where the hole will be drilled with masking tape first. Also if possible run the drill in reverse until it cuts though the gelcoat, especially when using a hole saw.

The Forstner bit would prevent the chipping. You could run the brad point slowly in reverse to start the hole. The centre point will keep the bit in position and it will score the fibreglass a apposed to chipping and then run it forward.